• 대한화학회지
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• 제42권1호
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• pp.42-50
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• 1998

산화티탄을 전극 재료로 사용하기 위해서는 투명하고 수용액에 안정한 재료가 필요하다.아세틸 아세톤 티탄(IV)으로부터 분사방법을 이용하여 산화티탄의 안정한 박막을 얻었다. 결정 모양은 구형을 나타내었으며, 결정의 크기는 온도가 증가함에 따라 증가하였고 두께는 감소하는 경향을 나타내었다. XRD 데이타로부터 아나타제 결정이 400$^{\circ}C$ 에서부터 얻어지기 시작함을 관찰하였다. 440$^{\circ}C$ 에서 만들어진 산화티탄이 고유 광전류가 최대값을 나타냈으며 가시광 영역에서 광전류가 증가하는 결과를 나타냈다. 가시광 영역에서의 광전류는 프탈로시아닌의 흡수 스펙트럼과 같은 ${\lambda}$max 위치에서 얻어졌고 이와 같은 결과는 프탈로시아닌의 결정 특성에 따른 광전류 특성으로 나타났다.

• 한국자동차공학회논문집
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• 제16권1호
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• pp.64-70
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• 2008

Temperatures of engine head and liner depend on many factors such as spray and combustion process, coolant passage flow and engine related structures. To estimate the temperature distribution of engine structure, multi-dimensional computational fluid dynamics (CFD) codes have been mainly adopted. In this case, it is of great importance to obtain the realistic wall temperature distribution of entire engine structure. In the present work, a CFD-FEM coupling methodology was presented to address this demand. This approach was applied to a real large-size marine diesel engine. CFD combustion and coolant flow simulations were coupled to FEM temperature analysis. Wall heat flux and wall temperature data were interfaced between combustion simulation and solid component temperature analysis via translator by a commercial CFD package named FIRE by AVL. Heat transfer coefficient and surface temperature data were exchanged and mapped between coolant flow simulation and FEM temperature analysis. Results indicate that there exists the optimum cell thickness near combustion chamber wall to reasonably predict the wall heat flux during combustion period. The present study also shows that the effect of cell refining on predicting in-cylinder pressure during combustion is negligible. Hence, the basic guidance on obtaining the wall heat flux needed for the reasonable CFD-FEM coupling analysis has been established. It is expected that this coupling methodology is a robust tool for practical engine design and can be applied to further assessment of the temperature distribution of other engine components.

• 대한기계학회논문집A
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• 제21권5호
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• pp.791-799
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• 1997

The wear characteristics and wear mechanisms of plasma sprayed Al/sub 2/ O/sub 3/-40%TiO/sub 2/ and Cr/sub 2/O/sub 3/ deposited on casting aluminum alloy(AC4C) were investigated. Specimens were processed for various coating thicknesses. Ball on disk type wear tester was used for wear test. The scratch test on plasma sprayed coating surface showed that critical load to break the coating layer was greater than 40 N. The critical load increase with the increase of coating thickness of specimens. The friction coefficient of Cr/sub 2/O/sub 3/ coating layer was less than that of Al/sub 2/O/sub 3/-40%TiO/sub 2/ coating layer. The wear resistance of Cr/sub 2/O/sub 3/ coating layer was greater than that of Al/sub 2/O/sub 3/-40%TiO/sub 2/ coating layer. Microscopic observation of worn surfaces was made by SEM. SEM observation showed that the main mechanism of wear for Al/sub 2/O/sub 3/-40%TiO/sub 2/ coating layer was abrasive wear under 50 N. For the case of Al/sub 2/O/sub 3/-40%TiO/sub 2/ coating layer, as the surface cracks perpendicular to sliding direction propagated, the wear debris was generated in wear track. However, the main mechanism of wear for Cr/sub 2/O/sub 3/ coating layer was brittle fracture under 150 N.

• 한국강구조학회 논문집
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• 제18권5호
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• pp.643-654
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• 2006

본 연구에서는 iTECH 합성보 실험체에 대한 온도와 변형에 대한 내화성능을 ISO834 표준화재와 BS476-20 및 KSF2257 기준에 근거하여 평가하였다. 국내외적으로 복합구조의 내화성능을 규명하기 위한 연구는 지극히 미흡한 실정이며, 따라서 본 연구에서는 iTECH 합성보의 내화성능을 평가하기 위해 1.5m의 슬래브를 포함한 4..7m의 스팬길이에 대하여 실험을 수행하였다. 변수는 실험체의 단면크기, 피복재 보강방법과 보강두께, 그리고 하중비로 하여 내화실험을 수행하였다.

• 한국표면공학회지
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• 제29권6호
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• pp.862-868
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• 1996

Cadmium sulfide is commonly used as the window material for thin film solar cells, and can be prepared by several techniques such as sputtering, spray pyrolysis, close spaced sublimation (CSS), thermal evaporation, solution growth methods, etc. In this study, CdS films were deposited by thermal evaporation, close spaced sublimation, and solution growth methods, respectively, and the effects of the methods on physical properties of polycrystalline CdS deposited on ITO/glass were investigated. Also, the effects of variously prepared CdS thin films on the physical properties of CdTe deposited on the CdS were investigated. The thickness of polycrystalline CdS films was maintained at $0.3\mu\textrm{m}$ except for the solution grown CdS when $0.2\mu\textrm{m}$ thick CdS was deposited. After the deposition, all the samples were annealed at $400^{\circ}C$ or $500^{\circ}C$ in H2 atmosphere. To investigate physical properties of the deposited and annealed CdS thin films, UV-VIS spectro-photometry, X-ray diffractometry (XRD), and Auger electron spectroscopy (AES), and cross sectional transmission electron microscopy(XTEM) were used to analyze grain size, crystal structure, preferred orientation, optical properties, etc. The annealed CdS showed the bandedge transition at 510nm and the optical transmittance high than 80% for all of the variously deposited films. XRD results showed that CdS thin films variously deposited and annealed had the same hexagonal structures, however, showed different preferred orientations. CSS grown CdS had [103] preferred orientation, thermally evaporated CdS had [002], and CdS grown by the solution growth had no preferred orientation. The largest grain size was obtained for the CSS grown CdS while the least grain size was obtained for the solution grown CdS. Some of the physical properties of CdTe deposited on the CdS thin film such as grain size at the junction and grain orientation were affected by the physical properties of CdS thin films.

• 한국표면공학회지
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• 제42권1호
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• pp.1-7
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• 2009

Resistive heating sources are widely used to prepare thin films by vapor deposition because they are cheap, and easy to install and handle in vacuum system. Graphite is one of materials used to make the resistive heating source, but until now only limited applications have been possible as it reacts easily with evaporating materials at high temperature. In this study, evaporation characteristics of aluminum have been investigated by using graphite boat thermally treated with BN powder. The employed graphite boat has been prepared by spray-coating BN power onto the cavity surface of the boat and thermal treatment with aluminum in vacuum at the temperature of more than $1400^{\circ}C$. The voltage-current characteristics as well as resistivity changes of the graphite boat have been investigated during aluminum evaporation according to the applied voltage and time. The evaporation aspect has been picturized during flash evaporation for 40 seconds based on the characterization results. The evaporation rate of the graphite boat has been compared with that of BN boat. The graphite boat showed some different characteristics compared with BN boat, in that the evaporation occurred at the last stage of flash evaporation. The film appearance according to the applied voltage has been compared, and also the reflectance of the resulting film has been investigated according to the film thickness. It has been found that the graphite boat thermally treated with BN powder can be used for aluminum evaporation without problem.

• Biomolecules & Therapeutics
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• 제16권4호
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• pp.425-430
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• 2008

The objectives of this study were to prepare PLGA film onto the surface of the capsular tension ring (CTR) for controlled drug release and investigate the influence of plasticizers, the test drug and measurement conditions on flexibility of the film. Film solutions were prepared by dissolving PLGA, plasticizer (triethyl citrate, TEC or polyethylene glycol, PEG), test drug (dexamethasone) in ethyl acetate then films were prepared by spray coating and evaporation method. Then, the flexibility of PLGA film was determined by elongation test. The addition of plasticizer, PEG or TEC to PLGA copolymer caused a depression of glass transition temperature ($T_g$) and the elasticity of PLGA films increased. The addition of dexamethasone to the PLGA/TEC matrix decreased the flexibility of film. Dimensional factors of the PLGA films such as width and thickness were significantly influenced on flexibility of films and film length and elongation speed had no considerable influence on elongation of films. In this study, sufficiently flexible and stable PLGA films capable of being coated onto CTR could be prepared. This PLGA films can be used as a platform for local drug delivery.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.382-382
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• 2012

CIGS thin films have received great attention as a promising material for solar cells due to their high absorption coefficient, appropriate bandgap, long-term stability, and low cost production. CIGS thin films are deposited by various methods such as co-evaporation, sputtering, spray pyrolysis and electro-deposition. The deposition technique is one of the most important processes in preparing CIGS thin film solar cells. Among these methods, co-evaporation is one of the best technique for obtaining high quality and stoichiometric CIGS films. However, co-evaporation method is known to be unsuitable for commercialization. The sputtering is known to be very effective and feasible process for mass production. In this study, CIGS thin films have prepared by rf magnetron sputtering using a $Cu(In_{1-x}Ga_x)Se_2$ single quaternary target without post deposition selenization. This process has been examined by the effects of deposition parameters on the structural and compositional properties of the films. In addition, we will explore the influences of substrate temperature and additional annealing treatment after deposition on the characteristics of CIGS thin films. The thickness of CIGS films will be measured by Tencor-P1 profiler. The crystalline properties and surface morphology of the films will be analyzed using X-ray diffraction and scanning electron microscopy, respectively. The optical properties of the films will be determined by UV-Visible spectroscopy. Electrical properties of the films will be measured using van der Pauw geometry and Hall effect measurement at room temperature using indium ohmic contacts.

• 한국표면공학회지
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• 제42권2호
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• pp.86-94
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• 2009

Various types of multilayer coatings including Al/$Al_2O_3$ structure have been prepared on Nd-Fe-B permanent magnet to modify the morphology of the coating and to enhance the corrosion resistance of the magnet. Magnetron sputtering has been employed to make the multilayer coatings. $Al_2O_3$sputtering conditions were optimized in reactive sputtering by varying the deposition parameters. The formation of $Al_2O_3$ film was confirmed from the binding energy shift measured by electron spectroscopy for chemical analysis. 3 types of coating structures were designed and prepared by magnetron sputtering. The coating structures consist of (1) single Al coating, (2) modified coatings having oxide or plasma treated layer in the middle of coating structure, and (3) Al/$Al_2O_3$ multilayer coatings. Surface and cross-sectional morphologies showed that Al/$Al_2O_3$ multilayer grew as a layered structure, and that very compact Zone 3 like structure were formed. X-ray diffraction peak showed that the crystal orientations of multilayer coatings were similar to that of the bulk powder pattern. Hardness increased drastically when the Al thickness was around 1im in the Al/$Al_2O_3$ multilayer. From the salt spray test and pressure cooker test, it has been shown that the multilayer coatings showed good corrosion resistance compared to Al single or modified layer coatings.

• 한국표면공학회지
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• 제48권6호
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• pp.260-268
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• 2015

The thermal barrier coating (TBC) for inner wall of liquid-fuel rocket combustor consists of NiCrAlY as bonding layer and $ZrO_2$ as a top layer. In most case, the plasma spray coating is used for TBC process and this process has inherent possibility of cracking due to large difference in thermal expansion coefficients among bonding layer, top layer and metal substrate. In this paper, we suggest crack-free TBC process by using a precise electrodeposition technique. Electrodeposited Ni-P/Cr double layer has similar thermal expansion coefficient to the Cu alloy substrate resulting in superior thermal barrier performance and high temperature oxidation resistance. We studied the effects of phosphorous concentrations (2.12 wt%, 6.97 wt%, and 10.53 wt%) on the annealing behavior ($750^{\circ}C$) of Ni-P samples and Cr double layered electrodeposits. Annealing temperature was simulated by combustion test condition. Also, we conducted SEM/EDS and XRD analysis for Ni-P/Cr samples. The results showed that the band layers between Ni-P and Cr are Ni and Cr, and has no formed with heat treatment. These band layers were solid solution of Cr and Ni which is formed by interdiffusion of both alloy elements. In addition, the P was not found in it. The thickness of band layer was increased with increasing annealing time. We expected that the band layer can improve the adhesion between Cr and Ni-P.